LONG BEACH — Almost a week after a sewage spill forced beach closures on eastside shorelines, many beaches were still closed Friday.

Health officials said the sites could reopen as early as Saturday, after water tests Thursday were clear of contamination.

An estimated 1,000 gallons of sewage contaminated Alamitos Bay following a spill from a private sewer system that began Sept. 29.

The spill initially resulted in the closure Sunday of Mother's Beach and Marine Stadium. However, additional testing resulted in other beach closures in Alamitos Bay and parts of Seal Beach later in the week.

Ocean-facing beaches in Long Beach, as well as the Colorado Lagoon swimming area, remained open to public swimming.

The spill originated with a homeowners association complex at Bixby Terrace Drive area near Seventh Street and the Cerritos Channel, according to Long Beach Department of Health and Human Services environmental health specialist Nelson Kerr.

He said health workers have been testing the water daily, and they'll keep the recreational water areas closed until two consecutive test results show no contamination.

Earlier in the week, the Health Department was still finding "hot spots" of bacteria contamination, Kerr said. By Friday, the water quality was improving.

"The test results looked good," Kerr said about Thursday's samples.

Officials continued to keep close tabs on the situation Friday, taking samples from the impacted beaches to determine whether recreational areas could be reopened. That decision could be made by Saturday, Kerr said.

The spill has been attributed to the failure of a sump pump at the private sewer system, Kerr said. Health officials believe that the spill began at about 7 p.m. Sept. 29.

City officials said they are taking action to prevent a similar another spill.

"The city will be aggressively pursuing actions to identify any and all contributing factors of the spill and considering the necessary and appropriate enforcement actions against the private property owner to prevent a future occurrence," city spokesman Ed Kamlan said.

Kerr said the investigation will include the sump pump's maintenance procedures, back-up system and alarm.

"This is not a common occurrence," Kerr said, adding that this was the first time these beaches have been closed this year.

Determining the potential cost for the city services is "in motion," Kerr said.

That's because the work is still on-going. The spill, Kerr explained, prompted the city's full response, including heath and water officials, firefighters and lifeguards, along with installing warning signs and conducting the daily lab tests.

"This is a very high priority item with our city leaders," Kerr said.

The Health Department posted warning signs that the Alamitos Bay beaches were closed, and lifeguards have been enforcing the closure, Kamlan noted.

At the Bay Shore Avenue beach Friday, a lifeguard patrolled the vacant sand, alerting one visitor that the waters were off limits. The visitor said he would go to a nearby ocean-facing beach a couple of blocks away.

The spill occurred during an unseasonably hot weekend when high temperatures increased the beach crowds. However, the lifeguard, who declined to give his name, said he has since seen a small number of would-be swimmers who have had to warned away from the water as summer draws to an end.